You could use pressure treated timber from a fence supplier; 4"x4" 6' or 8' tall, set into concrete bases. But these would not last as long as scaffold poles, again set into concrete. Fastening chain to the pole would be tricky, Alan is right about sourcing chain from Agricultural suppliers, but you would need some hefty bolt cutters to cut it to size unless the suppliers did it for you.

I guess you would have to drill through the top of the pole, attach a large bolt/hook with a nut and attach your chain.

...Skarlett, to post a photo click on the tree icon above where you are typing and then follow instructions. I find it best to pick out the photos I want to post first so I know where to find them (files and tags etc are a bit of a closed book to me)

Roast Autumn veg; Beetroot peeled and chopped into 4 or 6, Pumpkin; scrub the skin well with veg brush cut open de-seed and chop into larger bits than the beetroot (think about what cooks slowly and cut it smaller) Red onions, peeled and cut into 4 or 6 wedges, 6 or 8 garlic cloves un-peeled. And then any other veg that needs using especially if it is a hot colour.

Heat oven to 180 with large roasting tin. Pour veg into tin with large slurp of olive oil and loads of fresh herbs stripped off their stalks, mix well, roast until beetroot is tender, stirring once (about 40 mins). This can be eaten now...frozen now....added to stock in blender and made into incredible soup